This invention relates generally to the detection of voids and particulates in a flowing stream of fluid.
The detection of voids and particulates in a flowing stream of fluid is of interest in several industries. For example, the detection of small particulates in photoresist is important for the semiconductor industry. Although these fluids are filtered, contaminants may be dislodged from walls by shock or other means. Impurity monitoring is needed to determine the cleanliness of storage tanks. In the medical arts it would be useful to monitor fluids pumped outside the body such as in a kidney dialysis machine. In the metals industry, small particles of oxides and gas bubbles in molten streams must be monitored to improve quality control.
The invention is particularly useful for detecting voids and particulates in the liquid metal coolant (sodium) of a fast breeder reactor. Although sodium has many advantages as a coolant, it is difficult to work with. It is reactive chemically and must be kept dry at all times. When water from the water-sodium heat exchanger leaks into the sodium, the resultant reaction produces hydrogen bubbles and sodium oxide particles. The principle prior art leak detection technique detects the presence of hydrogen dissolved in the sodium. Hydrogen is detected by the diffusion of hydrogen through a nickel membrane. Although the sensitivity of this technique is good, the response time is slow and the technique does not distinguish leak hydrogen from extraneous hydrogen which may be present in the system after tube cleaning and during initial operation. Also, since both particulates and gas bubbles are generated by a leak, a detector which detects both particulates and voids will enhance leak detection reliability.
Various acoustic techniques are also available, but are sensitive to background noise level changes from temperature fluctuations, which affect the transducer output.
Therefore, it is an object of the present invention to provide a method and apparatus for detecting voids and particulates in a flowing stream of fluid.
It is also an object of the present invention to provide a method and apparatus which distinguishes voids from particulates in a flowing stream of fluid.
It is another object of the present invention to provide a method and apparatus for detecting voids and particulates which are insensitive to temperature fluctuations.
It is yet another object of the present invention to provide a method and apparatus for detecting leaks in the liquid sodium coolant of a breeder reactor.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by practice of the invention.